nil?

[tom]

How do you remove a nil from a list?

[m i c h a e l]

Tom,



Would this be what you are looking for?

Code Select Expand

> (clean nil? '(1 2 3 nil 4))
(1 2 3 4)


m i c h a e l

[tom]

I thought so.  trying it now, that works fine, but I have a list with both empty and nil elements, and clean seems to balk at the empty ones.  Here's what I get:

Code Select Expand


> box
("" nil "" "sdc1" "sda1" "sda2" "sdb2" "sdb1")
> (clean nil? box)
("" "" "sdc1" "sda1" "sda2" "sdb2" "sdb1")
> (clean empty? box)

ERR: list or string expected in function empty? : nil
>


EDIT



Ok, clean must not be destructive.

Code Select Expand


> (set 'box2 (clean nil? box))
("" "" "sdc1" "sda1" "sda2" "sdb2" "sdb1")
> (clean empty? box2)
("sdc1" "sda1" "sda2" "sdb2" "sdb1")
>


[m i c h a e l]

We could also cut out the box2 middle-man by using the result of the first function call as the argument to the second function:

Code Select Expand

> (set 'box '("" nil "" "sdc1" "sda1" "sda2" "sdb2" "sdb1"))
("" nil "" "sdc1" "sda1" "sda2" "sdb2" "sdb1")
> (clean empty? (clean nil? box))
("sdc1" "sda1" "sda2" "sdb2" "sdb1")
> _


Sorry if you already know this, but someone new to functional programming may not :-)



m i c h a e l

[tom]

:-)

[cormullion]

Or

Code Select Expand

> (set 'box '("" nil "" "sdc1" "sda1" "sda2" "sdb2" "sdb1") )
("" nil "" "sdc1" "sda1" "sda2" "sdb2" "sdb1")
> (clean (fn (e) (or (nil? e) (empty? e))) box)
("sdc1" "sda1" "sda2" "sdb2" "sdb1")
>


[Lutz]

Or use 'null?' which checks for the nil, the empty list (), the empty string "" and 0 and 0.00 and NaN.

Code Select Expand

> (set 'box '("" nil "" "sdc1" "sda1" "sda2" "sdb2" "sdb1"))
("" nil "" "sdc1" "sda1" "sda2" "sdb2" "sdb1")
> (clean null? box)
("sdc1" "sda1" "sda2" "sdb2" "sdb1")
>


[DrDave]

Or use 'null?' which checks for the nil, the empty list (), the empty string "" and 0 and 0.00 and NaN.

Thanks for pointing out 'null?' As you know, I've read the entire user's guide more than once, but didn't recall 'null?'

[cormullion]

It's hidden between now and nper... :)

[DrDave]

It's hidden between now and nper... :)

Ah, maybe I missed it becasue I'm not used to seeing alphabetical ordering such as

'npv'

'nth'

'null?'

'nper'  <---(how did this guy cut in line here??)

'number?'

[cormullion]

It's hidden between now and nper... :)

Ah, maybe I missed it becasue I'm not used to seeing alphabetical ordering such as

'npv'

'nth'

'null?'

'nper'  <---(how did this guy cut in line here??)

'number?'

This would help to find the queue jumpers, but I think the original is not HTML...?

Code Select Expand


(set 'file (read-file "/usr/share/doc/newlisp/newlisp_manual.html"))
(set 'data (find-all (string {<h2><span class="function">([a-z].*?)</span></h2>}) file   $1))

(map (fn (x y)
  (if (!= x y)
   (println (format { ? %-18s should be %-18s } x y))
   (println (format {   %-18s           %-18s } x y))))
  data
 (sort data))

.....
   nil?                         nil?              
 ? not                should be normal            
 ? normal             should be not                
   now                          now                
 ? null?              should be nper              
 ? nper               should be npv                
 ? npv                should be nth                
 ? nth                should be null?              
   number?                      number?    
.....



[Lutz]

The original is in HTML. I updated this copy:



http://www.newlisp.org/downloads/newlisp_manual.html">http://www.newlisp.org/downloads/newlisp_manual.html



yesterday and today, and all changes will also show up in 9.9.5

[cormullion]

Oh yes - it's the PDF that takes the time to generate from the HTML source, not the other way round. Sorry Lutz!